Automatic compression release



May 12, 1970 F. B. E STY 3,511,219

AUTOMATIC COMPRESSION RELEASE Filed Nov. 12, 1968 QZtorrzegS' United States Patent 3,511,219 AUTOMATIC COMPRESSION RELEASE Francis B. Esty, Brookfield, Wis., assignor to Wisconsin Motors Corporation, Milwaukee, Wis., a corporation of Wisconsin Filed Nov. 12, 1968, Ser. No. 774,673 Int. Cl. F011 13/08 U.S. Cl. 123-182 2 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to an automatic compression release for a multi-cylinder engine. A single, centrifugally actuated flyweight turns a rotor co-axially within a hollow cam shaft. The rotor has cam mean proximate certain cams on the shaft which actuate tappers for certain valves. There are radially movable push pins for each such tapper, the pins being actuated by the cams on the rotor, to simultaneously provide compression release for all cylinders at low engine speed and normal compression at high engine speeds.

BACKGROUND OF THE INVENTION My U.S. Pat. 3,362,390 shows an automatic compression release best adapted for incorporation into single cylinder engine. The present invention extends the principle of my prior patent to multi-cylinder engines.

SUMMARY OF THE INVENTION In accordance with the present invention, mechanism is provided to transmitthe turning moment of a centrifugally actuated flyweight to concurrently influence the tappers for a valve of each cylinder of a multi-cylinder engine. The flyweight is in motion transmitting connection to a rotor or shaft co-axial within a hollow cam shaft. Proximate each cam for the tapper of each such valve, there is a radially movable push pin, and cam means on the rotor for each pin. Accordingly, all push pins are moved simultaneously when the flyweight turns the rotor in response to changes in engine speed.

The disposition of the rotor shaft co-axially within the cam shaft provides for opening each such valve the same amount, under control of a single flyweight. The motion transmitting parts are completely housed within the cam shaft and are not exposed to possible damage and do not interfere with the functioning of other parts of the engine.

Other objects, features, and advantages of the invention will appear from the following disclosure.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary cross section through the cam shaft and associated cams and tappers of a multi-cylinder combustion engine. An exhaust valve and its seat are also shown in reduced scale.

FIG. 2 is an end view of the cam shaft driving gear with flyweight mounted thereon. In this view the engine is at rest or is turning at low speed, such as during cranking and at which time the compression release is effective.

FIG. 3 is a cross section taken along the line 3-3 of FIG. 2, the parts being shown in low speed position.

FIG. 4 is a view similar to FIG. 2 but showing the high speed position in which the flyweight is moved centrifugally outwardly to automatically de-actuate the compression release.

3,511,219 Patented May 12, 1970 DESCRIPTION OF THE PREFERRED EMBODIMENT Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto.

The function and purpose of the present invention are comparable to those stated in my prior patent aforesaid. FIG. 1 illustrates, for purposes of exemplification, a twocylinder engine. The invention is applicable to any multicylinder engine, regardless of the number of cylinders. Cam shaft 10 is driven by gear 11. A typical exhaust valve for one of the cylinders is shown in reduced scale at 12. This valve has a stem 13 having at its lower end a tapper or pad 14 which conventionally is spring pressed against cam 15 on the shaft 10. The stem 16 with tapper 17 of another exhaust valve of a second cylinder of the engine is shown near the right hand end of FIG. 1. Tapper 17 is spring pressed against cam 18. The valve stems 20, 21 are for the intake valves of the engine cylinders. Their action is not affected by the invention.

Compression release mechanism is provided for each of the exhaust valve tappers 14, 17. This mechanism comprises a shaft or rotor 22 which is disposed co-axially within a hollow bore 23 of cam shaft 10, and rotates therewith. Adjacent the respective cams 15, 18 are radially movable push pins 24, 25, disposed in radial bores 26 formed laterally through one side of the shaft 10. Each pin has a head 27 aligned with a flat or like cam means 30 formed on the rotor shaft 22.

The end of the rotor shaft 22 is provided with a crankarm 31 which is embraced by the fingers 32, 33 of centrifugal flyweight 34. Flyweight 34 is pivotally connected to the plate or gear 11 on a pintle 35. The flyweight 34 has a spring 36 which biases the weight toward the center of rotation of the gear 11, but which will yield under centrifugal force as the speed of the engine rises. At low speed, for example, any speed below about 650 rpm, the flyweight 34 will be in its position shown in FIG. 2 in which the cam flats 30 on the rotor 22 are turned away from the heads 27 of the pins 24. Accordingly the pins are lifted on the periphery of the shaft 22 to project to their maximum extent. The tappers 14, 17 will ride on the projected pins 24, thus to keep the exhaust valves slightly open during starting of the engine and effectuate compression release.

As engine speed increases above a predetermined speed, such as, 650 rpm, centrifugal force will turn the weight 34 outwardly about pintle 35 and against the pressure of spring 36 to its position shown in FIG. 4, whereupon the fingers 32, 33 will act on the crankarm 31 of the rotor shaft 22 to turn the rotor shaft to its position shown in FIGS. 4 and 5. The pins 24, 25 may now retract under the pressure of the tappers 14, 17 into the space above the cam flats 30, thus to permit the exhaust valves to close completely during the charging cycle of the engine.

The push pins for both tappers 14, 17 will be actuated simultaneously to effectuate equal compression release for all cylinders at low speeds and to de-actuate the compression release for all cylinders simultaneously at higher speeds. A single rotor turning mechanism comprising the 4 centrifugal weight 34, etc., turns the rotor 22. By mountrotor turning mechanism responsive to engine speed for ing the rotor 22 within the hollow cam shaft, it is out of concurrently actuating each said push pin. the way of other engine apparatus. 2. The engine of claim 1 in which said rotor turning It is claimed: mechanism comprises a single centrifugal flyweight. 1. -In a multi-cylinder engine having a cam shaft, cams and tappers actuated by said cams, the improvement in 5 References Cited an automatic compression release which acts concurrently UNITED ATES PATENTS on a tapper for each cylinder and comprising:

said cam shaft being hollow and having co-axially thereg 123 182 within a rotor which extends along the cam shaft 10 ampen into proximity to the cam for each said tapper, FOREIGN PATENTS radially movable push pins mounted in said cam shaft 527 393 4 19 Great Britain and cooperating with each said tapper, 1 109 790 9/1955 France.

cam means on said rotor for actuating each said push pin, and 15 CARLTON R. CROY'LE, Primary Examiner 

